1. Field of the Invention
The present invention generally relates to a copolymer resin, more particularly the present invention relates to an improved functional multilayer anisotropic conductive adhesive film (ACAF) and its preparation method.
2. Background of the Invention
A need for reduced weight and thickness has recently arose in connection with electronic equipment and devices containing mounted IC chips because of new developments related to such electronic equipment, and there is also a need of functional connection stuffs for higher density in boards for mounting such IC chips. For example, in order to set micro fillets directly engaged with IC chips, flexibility of the connection stuffs is necessary for higher density in boards for mounting such IC chips, thus anisotropic conductive film (ACF) is applied for this purpose. For the moment, ACF market scale is over 20 billions, and playing an important role in social development.
During research and development of the ACF, in a typical pencil anisotropic conductive film, fillet distance and fillet width is about 100 microns. TAP and COG apply different adhesive resins, coupling agents, and silicon powder fillers, which is disclosed in Japan Patents, JP03129607, JP08325543, and JP0931419. Other conventional preparation method for ACF is disclosed in patents, such as CN99807810.7, U.S. Pat. No. 5,240,761, U.S. Pat. No. 4,113,981, U.S. Pat. No. 5,180,888, U.S. Pat. No. 5,240,761, and U.S. Pat. No. 4,737,112, which says that: defining a plurality of dimples on a resin film, placing conductive balls in dimples and then carrying coating process, thereby forming films demanded.
Assembling component without punching and welding is the key to realize high density fillet deployment, high speed connection and ultrathin assembly goals. However, on condition that fillet width of IC chips to be connected is about 100 microns, the conventional ACF can barely meet such connection needs. Therefore anisotropic conductive adhesive films (ACAF) play an important role in connection between IC chips or IC chips based on transparent substrates and high density FPC or COF. Researches on ACAF synchronizing with development of IC chips focus on optimum preparation processes and stuff preparation so as to improve connection property and lower cost. Meanwhile development of ACAF will facilitate expansion of LCD market.
A typical ACF can refer to multilayer or two layer ACF, adopting layer to layer affixing means which is disclosed in Japan application No. 2001171033, it says first and second layers are tapes formed by coating process with resins in different proportion. Furthermore, Japan application No. 2001178511 discloses that four coating processes are presented, a typical ACF is formed with first multilayer anisotropic conductive adhesive layer, second insulating layer, third anisotropic conductive adhesive layer, and fourth insulating layer. However, ACF obtained from the conventional preparation means mentioned above can hardly meet chip connection needs on condition that chip fillet width is 10 microns.
In light of the foregoing, there is a very desirable need to improve the typical anisotropic conductive adhesive film.